Hypoxemia is a life threatening event that frequently occurs in all patient care areas, especially in operating room (OR), procedural room outside the OR, post anesthesia care unit (PACU), emergency room (ER), and intensive care unit (ICU) settings. Patients in these settings either receive medications (such as anesthetics, analgesics, and sedatives) that can cause apnea and respiratory depression or have acute or chronic diseases that can cause hypoxemia. Supplementing oxygen or providing assisted ventilation is an essential approach to avoiding hypoxemia and maintaining adequate oxygenation.
A wide variety of devices, such as nasal cannula, face mask, and nasal mask, are available to deliver oxygen therapy for non-intubated patients. Face masks and nasal masks are commonly used to deliver high flow of oxygen but are not well tolerated by patients (especially those patients with claustrophobia). To deliver high concentrations of oxygen, a good mask-to-face/nose seal has to be attained and the pressure on the nose and face causes considerable discomfort for a patient. A nasal cannula is a simple, benign, and inexpensive device. It is widely used and well tolerated by the majority of patients and valuable for patients who do not require a high Fraction of Inspired Oxygen (FiO2) and who are unable to tolerate face or nasal masks. However, existing nasal cannulas allow neither administering high flow of oxygen, since they can only provide a flow rate of oxygen up to six liters per minute (lpm), nor do they provide assisted ventilation. Existing nasal cannulas are inefficient for delivering gases because most of the delivered gases are wasted and only a small percentage of the delivered gases actually reach the nasal airway of a patient. Additionally, the suction force generated by a gas analyzer draws the mucosal tissues onto the tip of nasal prong, and causes frequent occlusion, itching and discomfort. They are also easily dislodged and moved away from the nostrils of a patient.
To overcome some drawbacks of a conventional nasal cannula, several modified nasal cannula systems have been proposed to improve the efficiency of oxygen delivery or to deliver high flow of oxygen. The reservoir nasal cannula by Tiep et al., disclosed in U.S. Pat. No. 4,535,767, and marketed by Chad Therapeutic, Inc, known as the Oxymizer (trademarked), mustache style and pendant style, has a small reservoir (about twenty milliliters volume) to store oxygen during exhalation and save oxygen. The ability to conserve oxygen is limited due to the limited volume of the reservoir and the air dilution during the inhalation.
Another oxygen delivering and conserving device, proposed by Abel in U.S. Pat. No. 5,280,780, has a larger oxygen storage chamber and does not allow exhaled gases to mix with delivered oxygen. Abel's device may save more oxygen during exhalation and allow delivering higher concentration of oxygen. However, the nasal prongs of the devices of both Abel and Tiep et al. are open to the air and cannot avoid the dilution of oxygen from the air entrain during inhalation. Thus, they do not allow administering high flow of oxygen to meet a patient's need.
Another nasal cannula, disclosed by James Chua in US published patent application 2014/0276169 A1, has divided flow paths allowing insufflating oxygen through one of the nostrils and collecting the exhaled gases from the other nostril. The nostril that is used for insufflating gases is blocked by an insufflating nare with a one-way valve, which allows supplying oxygen from the insufflating nare during inhalation only but not during exhalation. The other nostril is dedicated for sampling the exhaled gases via a sampling nare that does not block the nostril. This device allows delivering low flow of oxygen and conserving oxygen while allowing sampling an undiluted sample of end tidal carbon dioxide (ETCO2) contained within the exhaled gases from the patient. However, it does not provide other desired functions, such as delivering high flow of gases, attaining CPAP and providing positive pressure ventilation.
The Optiflow (trademarked) nasal cannula interface, manufactured by Fisher & Paykel Healthcare Inc., is for delivering high flow of air/oxygen to a patient's nose. This delivery system can deliver heated and humidified air/oxygen by a device called the “AIRVO 2” (trademarked) at a rate of two to sixty liters per minute (lpm) and provide nasal insufflation. Nasal insufflation with high flow of air/oxygen has shown several beneficial effects, such as decreasing work of breathing, improving ventilation efficiency, reducing the need for intubation in patients with respiratory insufficiency, and preventing post-extubation failure. The exact mechanisms are unclear but it builds up CPAP and can treat mild and moderate sleep apnea. The “AIRVO 2” (trademarked) has been used for pre-oxygenation and apneic oxygenation during routine anesthesia induction or emergency intubation and significantly decreases the incident of hypoxemia during efforts securing an endotracheal tube. It has also been shown that initiation of nasal insufflation with high flow of air/oxygen immediately following extubation reduces the risk of reintubation. Although post-extubation non-invasive ventilation (NIV) remains the first-line approach when indicated, nasal insufflation may be an attractive alternative to NIV for patients who aren't candidates for post-extubation NIV or who are unable to tolerate NIV. Unlike NIV, nasal insufflation allows patients to talk and expectorate secretions. However, the Optiflow (trademarked) nasal cannula is open to air (occludes no more than 50% of a nostril) and high flow rates of oxygen are required to prevent air entrain during inhalation. A special device that can heat and humidify the air/oxygen is required and not readily available in all of the patient care areas.
Obstructive sleep apnea (OSA) is a common sleep disorder that occurs when a person's breathing is interrupted during sleep. The patients with OSA have a significantly increased risk of respiratory complications perioperatively. Continuous positive airway pressure (CPAP) and other non-invasive positive pressure ventilation (NIPPV) techniques have demonstrated clinical benefits in patients with OSA and have become the standard of care in the hospital environment. A CPAP system typically consists of a CPAP machine (a gases supply), a conduit tube, and a nasal or face mask. The nasal or face masks are uncomfortable to wear because of the pressures applied on the face and the nose. Several nasal interfaces have been proposed to replace nasal or face masks for attaining CPAP. They are more comfortable to wear and have increased patient comfort and compliance. These nasal interfaces include Nasal Aire II (trademarked) (invented by Thomas J. Wood and manufactured by InnoMed Technologies, Inc), Bravo (trademarked) nasal pillow CPAP mask (invented by and manufactured by InnoMed Technologies, Inc), Swift™ FX (trademarked) nasal pillow (manufactured by ResMed) and AirFit P10 (trademarked) nasal pillow (ResMed). They completely seal the nostrils and prevent air leakage during inhalation and exhalation. They can attain CPAP and provide positive pressure ventilation if needed. However, they are designed for delivering CPAP and treating OSA. A CPAP machine is needed. It is also difficult to deliver high flow of oxygen via these nasal pillows without significant modifications. Most of conscious patients may be not comfortable with both nostrils being blocked. Another nasal interface (NVA SNOR-TAL® (trademarked) options, by Noble Anesthesia-Air Inc.) is designed for delivering positive airway pressure from an anesthesia circuit. It is self-sizing, self-retaining and self-sealing within the nasal vestibule (from the company's website). It also gives the anesthesia practitioner unencumbered access to the mouth. One of the major disadvantages is that it has to be used with an anesthesia circuit and cannot be used in the settings without an anesthesia machine.
In summary, existing nasal breathing devices can only provide one or two desired functions and do not have multifunction to meet the requirements of patients and clinicians. Thus, there is a need for a single nasal breathing device that can have multifunction to meet the patient's needs.